Professional Mobile Radio (PMR), also known as land mobile radio (LMR) in North America and private mobile radio (PMR) in the UK, was developed for business users who need to communicate over relatively short distances with a central base station/dispatcher. PMR systems may be used in military, oil and gas, public security, rail transport, emergency, and various other applications.
PMR systems have generally been based on analog technology. To increase spectrum efficiency as well as improve communication quality, various jurisdictions plan to migrate from analog to digital PMR/LMR.
DMR (Digital Mobile Radio) is a digital radio standard for Professional Mobile Radio (PMR) systems. Requirements of the DMR standard include a channel spacing of 6.25 kHz, and a spurious emission specification of −83dBc (dB relative to the carrier).
The frequency synthesizers employed in digital radio systems often employ a phase locked loop to generate radio frequency signals.